1. Field of the Invention
The present invention is related to telecommunications network call connection management and call setup systems. More particularly, the present invention is related to control of ancillary telecommunications devices (e.g., echo cancelers, etc.).
2. Description of the Related Art
Modern telecommunications networks consist of a number of switching systems which are connected together via various transmission facilities. An example of a problem associated such networks faced by many providers is service quality and, in particular, the need to control echo. Echo is a transmission impairment that is related to delay, which in turn is a function of distance. To date, echo control devices external to the source have been installed in telecommunications networks to mitigate echo impairment.
Telecommunications networks have the ability to transport both voice-band applications (analog) and digital data applications via switching and interconnected transmission links. The problem arises when a network must pass digital data applications over the same transmission links as those used for voice and voice-band data and an echo control device is encountered. These echo control devices used in voice networks are installed to correct the impairments caused by delay. A voice-band data application will utilize its own means of controlling echo control devices. However, the digital data calls lack this same means.
Typically, in many telecommunications networks call connections are initiated and setup using two basic forms of signaling. The first is what is known as Channel Associated Signaling (CAS) and the other in Common Channel Signaling (CCS). Neither method provides for any type of discrimination between voice-band and digital data connections.
In a CAS environment, signaling bits are used to signal between switches to alert and establish calls. These signaling bits are also used by ancillary equipment that may be in the call path as an indication of an incoming call. Such devices monitor signaling bit status and respond accordingly. This type of signaling is referred to as robbed bit signaling, as part of the payload is used as signaling bits.
The CAS response to the onset of a call is that signaling bits respond in accordance with the trunk signaling requirements and not the requirements of the call type.
In a CCS signaling environment, the signaling for call setup is passed between network switches on a disassociated channel. In this signaling mode, the bearer (communications) channel retains all of the payload bits for the transmission of the payload.
There are certain abilities within a CCS system whereby the originating switching system does have an understanding of the call type at the onset of the call based on the properties of the originating connection type. These call types can be transmitted to any other switching system within a network in order to establish a call connection. The problem remains in that ancillary equipment such echo cancelers are stand alone devices that may not have connections to the switching system and therefore cannot be instructed to assess the nature of the connection type.
With the onset and deployment of CCS signaling, the inherent continuity testing based on in-band signaling response provided for an adequate means to ensure end-to-end circuit integrity. However, CCS signaling no longer uses the signaling bits to establish call connections. This mode uses an external link to transport call connection status between the network switches. In this mode there are no defined signaling bits, which in turn frees up these bits. Ancillary equipment must now rely on the detection of idle codes within the payload to detect the onset of a next call event.
In order to address the possibility of alarm masking due to multiple transmission types deployed in a network, the addition of COT (continuity test) tones was deployed during call setup to ensure transmission channel integrity. For the sake of clarity in the following examples defining the embodiment of the invention HI tone will be assigned for voice band connections whereas LO tone will be associated with connection for digital data. It is further understood that additional tones could be used to address additional levels of control for devices other than the exemplar echo control devices discussed in the following examples. The CCS mode still has the same problem inherent with CAS in that the operation of any ancillary equipment in the call connection can not be modified once prior to or once the connection is established.
COT tones and tests are well known and are defined in industry standards documentation identified as ITU-T Q724 for use on a four wire circuit as being a 2000 Hz tone, and for two wire circuits as being a 1780 Hz tone. In as much as two tones have been defined, this application designates the first tone as xe2x80x98HIxe2x80x99 and the second as xe2x80x98LOxe2x80x99.
The following describes other methods for extending call by call control to ancillary equipment. These methods have both merit arid limitation that may preclude their use in a wide spread manner.
The use of the Facility Data Link (FDL) is being pursued in industry standards bodies as a means to address call by call control, but this implementation would require a network that supports an Extended Super Frame line formatting.
Another possible solution is the use of an external control link for the switch platform to the ancillary equipment. This would provide the necessary control function, but introduces several other issues such as cable management and records keeping issues that would be substantial for a large-scale implementation.
Accordingly, there exists a need to provide new and improved systems and methods that will permit better, more reliable control of ancillary telecommunications devices such as echo cancelers, etc. To be viable such systems and methods must permit wide-spread deployment without causing undue and expensive infrastructure enhancements.
System and method for controlling a telecommunications device such as an echo canceler within a telecommunications system. The system and method include and involve a switching system that is configured to receive a call from a calling station and to route said call within said telecommunications system, and an ancillary telecommunications device that is configured to control a call processing parameter to affect said call. The switching system and the ancillary telecommunications device are coupled to each other via a channelized call data network. The channelized call data network is configured to communicate data corresponding to the call over at least one data channel. The ancillary telecommunications device may control the call processing parameter to affect the call based on a continuity test issued by the switching system to the ancillary telecommunications device prior to and during the call.